1. Technical Field
The present invention relates to an optical disk drive and, more particularly, to control of recording power.
2. Related Art
Recording power used during recording of data into an optical disk is controlled while a β value is principally taken as an index. Specifically, a β value, which is to serve as a target value, is previously determined for an optical disk to be recorded. Recording power is controlled in such a way that a β value measured after data have been recorded in an optical disk comes to a target β value.
JP 2010-500700 A discloses measuring a target β value for an inner radius and another target β value for an outer radius of an optical disk and subjecting these target β values to linear interpolation, thereby calculating target β values for respective speeds (i.e., at respective radial positions) in a data area on the optical disk.
JP 2003-115110 A discloses performing optimum power control (OPC) at a plurality of speeds when OPC in an inner radius of an optical disk to thereby measure target β values and carrying out interpolation by means of linear interpolation for recording speeds at which measurement has not been performed, to thus calculate target β values.
When recording power is controlled in such a way that a β value determined through measurement matches a target β value, control must be based on premise that the measured β value is accurate. However, an error can arise in a measured β value for various reasons. For this reason, a proposed procedure is for controlling recording power by use of a reference optical disk in a production line before shipment of optical disk drives in such a way that all of the optical disk drives provide the same measured β value, and making a correction when data are actually recorded on an optical disk by use of the control value. However, there is no guarantee that a match will exist between conditions for performing control in the production line and conditions for actually recording data. For instance, variations can arise in temperature and speed during recording operation, which raises a problem of the correction being insufficient.